The present invention is related to means for the stabilization of the line of sight between an object and an optical viewing system, which move relative to one another.
It is conventional to stabilize systems by producing, first of all, with the aid of the gyroscopic principle, a space-bound rotational reference system and, with the aid of detected values of path length, velocity, or acceleration, a space-bound translational reference system. Deviations are determined in the positions of the devices from these reference systems; and the original position is restored by means of control elements.
When such a device consists, for example, of a viewing instrument, translational movements can be neglected. In such a case, a triaxial angular stabilization with gyroscopes is sufficient. These principles exhibit the disadvantage, on the one hand, that the frequency range of around f =o is obtained only asymptotically, for example, in case of a sinusoidal angular movement of the observer with respect to the object, due to gyroscopic errors. A further disadvantage is the space-bound stabilization, since this does not cover the movement of the object relative to space. In many practical cases, it is only important for stabilizing purposes that a specific axis, e.g. the line of sight of a telescope, the position of which is determined by the device to be stabilized, i.e. by the observer, always pass through the object of interest.
A further problem in an optical viewing apparatus used in vehicles which are subjected to strongly varying accelerations resides for the observer, in that the pupil of the observer's eye must be kept within the exit pupil of the optical system. Attempts have been made to solve this problem by enlarging the exit pupil, and transmission to projection screens or even television screens. Also optical joints have been suggested. The aforementioned principles have the disadvantage that a practicable solution can be obtained only at considerable expenditure. Furthermore, there is no non-contactual direct coupling between the variable relative positions of the pupil of the eye and of the exit pupil.